Color facsimile system



June 24, 1947. w. G. H. FINCH 2,422,778

COLOR FACSIMILE SYSTEM Filed Feb. 15, 1945 2 Sheets-Sheet l JNVENTOR.W/LL/AM G. H F/NCH BYMMVM 4 A Tram/Em June 24, 1947. w. G. H. FlNCH2,422,778

COLOR FACS IMILE SYSTEM Filed Feb, 15, 1945 2 Sheets-Sheet 2 INVENTOR.W/LL lAM 61H. F/NCH Patented June 24, 1947 UNITED STATES PATENT OFFICECOLOR FACSIMILE SYSTEM William G. H. Finch, Ncwtown, Conn.

Application February 15, 1945, Serial No. 577,975

3 Claims.

My invention relates in general to the field of facsimile transmissionand more specifically to a novel method and means for transmitting andrecording pictures in natural color. In general, in facsimiletransmission, a signal is generated which corresponds to the variationsin the lights and shades of the picture which is transmitted.

This signal is transmitted in any convenient manner to a remote recorderand impressed upon a variable light source to selectively control theexposure of a photographic film.

The transmission. of pictures in natural color has heretofore generallybeen limited to a three color separation process, that is, the colorimage to be transmitted was scanned three times through filters of theprimary colors and three distinct color separation recordings were madeat the receiver. After development, the individual photographic filmswere properly dyed and superimposed to form a finished color image.

This type of color transmission process was necessarily lengthy andrequired, because of the triple transmission, extreme mechanicalaccuracy within the facsimile apparatus and precise synchronization, sothat the three-color separation negatives could be superimposedproperly.

My invention contemplates the utilization of natural color film such asKodachrome or Kodacolor for the direct recording of a transmitred colorimage.

In accordance with my invention, a color pic ture to be transmitted issuitably supported upon a scanning mechanism at the transmitter and isscanned by a novel color mechanism so arranged that each element of thepicture is scanned for a range of color covering substantially theentire color spectrum. Thus, instead of a threecolor analysis of apicture to be transmitted which has in many cases been found to be insuflicient for faithful reproduction upon Kodachrome film, I utilize aprism for dispersing a beam of white light into a complete colorspectrum, and scan the color picture with a multiplicity of color bandsobtained from this spectrum. For example, the scanning mechanismcarrying the color picture to be transmitted has each line of the imagescanned approximately eight times, each scanning operation utilizing adifferent color for the scanning spot. The particular color utilizedduring any single scanning of a line of the image to be transmitted iscom tinuously selected from the color spectrum above mentioned.

A photo-electric cell responive to light impulses over the completevisible spectrum picks up the r 2 light reflected from the image. andaccordingly develops an electrical signal which at each instant isproportional to the intensity of a particular color of the spectrum at agiven point in the picture.

At the recorder, the received signal is impressed upon a mechanism forgoverning the passage of light therethrough. This light valve controlsthe intensity of a beam of light dispersed by a prism in a mannersimilar to that described for the transmitter. The prism is continuouslyadjusted so that the color of light impressed upon the light valve isthe same as the color of light impressed upon the image at thetransmitter. Light passing through the light valve is impressed upon aKodachrome film mounted upon the receiving-scanning apparatus, and accordingly the colored light variation will record directly so that whenthe recording film is developed, a true Kodachrome reproduction of theimage transmitted is obtained.

It is therefore an object of my invention to provide means fortransmitting pictures in natural color.

A further object of my invention is to provide transmitting andrecording facsimile apparatus for producing a Kodachrome reproduction ofa colored image.

A further object of my invention is to provide means for scanning acolor image with lights of varying colors as obtained from a spectrumcevering the entire visible range.

A still further object of my invention is to provide a facsimile colorrecorder utilizing Kodachrome film which utilizes a prism as a sourceoflight of various required colors.

These and other objects of my invention will become apparent from thefollowing specification taken in connection with the accompanyingdrawings in which:

Figure 1 is a diagrammatic representation of my novel color transmitter,and

Figure 2 is a diagrammatic representation of a color facsimile recorder,and

Figure 3is an enlarged view of a slight modi fication of the cam memberOf Figures 1' and 2.

Referring now to Figure 1, there is shown a facsimile color transmitterwhich generates electrical signals that are at all times representativeof the color of a particular point of an image. Motor 2| drives ascanning drum 22 through a gear-ratio box 23 and extensible square shaft23'. The drum 22 is suitably supported upon a stationary screw 24 which,as will later be de scribed, causes lateral displacement of the drumduring the rotation of drum 22.

The image which is to be transmitted and which is in natural color, issuitably supported upon drum 22 by a mounting bar 25. The image 26 isscanned by a color scanning mechanism which is fixed to the frame of thefacsimile ap paratus. Thus continuou scanning is obtained by fixing thescanning apparatus 2'? and causing lateral displacement of the drumduring its rotation.

The color scanning apparatus 21 comprises essentially a lamp-house 3|enclosing a powerful white light bulb 32. The bulb 32 is preferably ahigh pressure, high intensity lamp which develops a balanced whitelight, such that Kodachrome when exposed to this light will photographwhite.

A vertical slit 33 at the front of the lamphouse 3| is focused bycylindrical lens 34 upon the surface 35' of a triangular prism 35.

As illustrated, the angle of incidence of the focused light rays is suchthat the prism 35 will cause the dispersion thereof into a uniformvisible light spectrum 36 covering the complete visible range from deepred to deep violet.

In the path of the dispersed beam of light 36 is a metallic plate 31having a small opening 4| which is preferably square, the width of whichis approximately A; the width of the visible spectrum 36 at the point ofincidence with plate 31.

The rectangular perforation 4| is sharply focused by optical system 42at a spot 43 upon the surface of the color image 26 to be transmitted.

Light reflected from the focused spot 43 upon the color picture 26impinges on photo-electric cell 45 enclosed in light-housing 44 by meansof a suitable optical system 46. Photo-electric cell 45 is preferablyone which has a uniform sensitivity to light throughout the visiblespectrum.

The output of photo-electric cell 45 is transferred through wires 41 toa suitable amplifier which raises the energy level of the signalgenerated to that suitable for transmission to a remote recorder.

The prism 35 is preferably of glass having a comparatively highdispersion and low absorption, in order to produce a spectrum 36 ofmaximum width and of great intensity when measured along the plate 31.The prism 35 is rotatably supported by vertical shafts such as cementedto the upper and lower surfaces thereof. These shafts are held insuitable fixed bearings which have been omitted from this diagram forclarity.

Also cemented to the lower surface of prism 35 is a link 52 of the shapeshown. A spring 53 attached to link 52 and fixed to the frame at theopposite ends thereof is utilized to bias the edge 54 of the link 52into engagement with the active surface of a cam 55.

As illustrated in this modification of the transmitter, the cam 55 is sshaped that upon rotation thereof, the edge 54 of the link 52 will bedisplaced outwardly from the cam center at a uniform speed until theedge 6| of the cam is reached, rotation being in the direction of thearrow indicated upon the surface of the cam.

Upon reaching the edge 6|, the cam follower edge 54 will, under theinfluence of spring 53,

swing back to its original position and begin its uniform outward motiononce again.

The depth of the cut 6| in the cam 55 and the size and position of link52 are so arranged that the prism 35 rotates through a comparativelysmall angle. This small angle of prism rotation however is suilicient tocause the spectrum of color 36 to sweep across the square perforation 4|in the fixed plate 31. Accordingly, for a single rotation of the cam 55,the spot 43 will continuously change color from deep red to deep violetas determined by the position of cam 55. Rotation of cam 55 is obtainedthrough gear-ratio box H which comprises essentially a pair of bevelgears to transfer the rotation of horizontal shaft E2 to vertical shaft13, to which the cam 55 is secured.

Rotation of shaft 12 is in turn secured from gear-ratio box 14 driven byshaft 15 which is connected to gear box 23.

The driving mechanism, as will later be described, for the drum 22 isarranged so that rotation of drum 22 about its axis takes place forpreferably eight revolutions before the drum 22 is displaced laterallyfor the thickness of a single scanning line as determined by the widthof the square perforation 4|. Thus, in the transmission of a colorpicture, the image 26 is mounted upon drum 22 and each circular lineabout the image is scanned eight times during which time the drivingmechanism for cam 55 causes one complete revolution thereof.

It will therefore be evident that during the eight scanning cycles foreach line of the image that the scanning color of the spot 43 projectedupon the image 26 is continuously varied from deep red to deep violet byrotation of prism 35. Accordingly, since the visible spectrum 36 isdivided into a multiplicity of color bands, each scanning cycle of thedrum is covered substantially by a different color of the spectrum 36.The light reflected from the spot 43 at any instant is proportional tothe component of the instantaneous color projected thereupon, andtherefore the output of photo-electric cell is at all timesrepresentative of the proportion of the intensity of a particular colorof the visible spectrum at the spot 43, since for a complete revolutionof cam all colors of the visible spectrum are covered.

The summation of the photo-electric cell output for a given point on thescanning line is equal to the true color for that particular point. Theoutput of photo-electric cell 45 is transmitted to a remote receiverwhich, as illustrated in Figure 2, is in most respects similar to thetransmitter of Figure 1.

As is well known in the facsimile art, it is essential to drive thefacsimile transmitter and recorder in synchronism with each other asregards both speed and space. Various methods, such as the use ofsynchronous motors or the sending of synchronizing impulses once duringeach revolution of the transmitting drum, are well known in the art ofsynchronization, and accordingly will not be described here.

It is assumed however that the transmitter and receiver of theparticular system described herein are operated in synchronism.

At the recorder (Figure 2), the motor |il| through gear-box W2,extensible square shaft .ifil and clutch I32 (which may be used in awcll-lmown manner for synchronizing purposes) 5 'ves the rotatable drum163 in the manner described for the rotatable drum at the transmitter;the rotation of drum Hi3 along stationary screw results in longitudinalmovement of the drum as it rotates. Similarly, the shaft I04 connectedto motor |0| through the gear-ratio box I02 drives the cam Hi5 at aspeed corresponding to anexact fraction of the speed of the drum I03.The gear-ratio boxes I02, I06 and ID'I are identical to the gear-ratioboxes 23, I4 and II respectively at the transmitter; and accordingly,the speed of cam N35 is identical to the speed of cam 55 at thetransmitter.

A. lamp-house IlI houses a powerful bulb H2 which is color-balanced sothat when Kodachrome" is exposed under the influence of this light, thecorrect color gradations are obtained.

At the recording apparatus, a slit I3 is focused by cylindrical lens II4 upon a prism II5 operably connected to the cam I55 by a link I IS.

A fixed metallic plate II"! has a rectangular perforation its thereinwhich by optical system IZI is focused upon a light valve I22. Thislight valve I22 an electrmmechanical means for varying the intensity ofthe light transmitted therethrough and may assume various forms as iswell known in the art. Thus an electro-magnetically operated shutter orother well known means may be utilized at this point.

. Light emanating from light valve IE2 is sharply focused at spot I23 onthe surface of the drum. [is illustratedin Figure 2, the drum H33 bymounting bar I3I- supports a sheet of Kodachrome or Agfa-color orKodacolor I32 or other color responsive photo-sensitive sheet which uponexposure to colored light may be developed to produce a colored image.

The received picture signals are suitably amplified by conventionalamplifiers (not shown) and are impressed by wires I33 upon the lightvalve I22. Therefore, the light valve I22 is responsive to the receivedpicture signals to control the intensity of the focused spot I23.

In actual operation of my novel natural color facsimile processillustrated, the image 26 to be transmitted is scanned as previouslydescribed. The identical scanning procedure at the recorder produces apicture which at all points represents the true color of the imagetransmitted. Thus, at the transmitter, each circular scanning line aboutthe drum 22 is scanned by spot 43 preferably for eight completerevolutions. During this continuous scanning of a single circular lineabout the drum, as previously described, the color of the scanning spots4-3 progressively varies from deep red to deep violet throughout thevisible spectrum, and accordingly the response of photoelectric cell 45is proportional to the intensity of the particular. color of lightreflected at each instance.

At the recorder, Figure 2, the multiple scanning of each circular lineof the Kodachrome or other color film I32 is again accomplished by aspot I23 which is varying in color in accordance with the colorvariations of the spot 43 at the transmitter, while simultaneouslyvarying in intensity through the agency of light valve I22, inaccordance with the intensity of the particular reflection of that colorat the transmitter.

At the termination of the scanning of a single circular line about aKodachrome image I32, the cam IE5 will have completed a singlerevolution and the prism II5 will be instantaneously re-set to scan thefollowing circular line with the complete color spectrum producedthereby.

It is evident that the multiple scanning at the receiver will provideeach circular line with all the color components required to reproduceexactly a color image. Of course, the number of scanning cycles of thedrums 22 and I32 may be varied dependent upon the desired quality oftransmission. Thus the cams 55 and I05 may be I0! to provide a singlerevolution, that is, a single" sweep of the spectrum produced by theprism in a fewer or greater number than the previously mentioned eighthcycle of the drum.

If a lower ratio between the number of revolutions of the drum, for asingle revolution of the cam, is desired, it is preferable to vary theshape of the cams I05 and 55 to that shown in Figure 3.

In this modification, since the cam MI is machined to have a series ofcircular edges, such as MI and MI", all concentric and all cut at evenlystepped radii, the direction of rotation of the cam MI is indicated bythe arrow I42, and the cam follower edge is schematically shown at I43.It will be understood that the cam follower I43 is the extension of thelink 52 or H6 connected to the prism and H5 respectively.

The corners, such as I44 between the successive steps of the cams MI andMI", have been rounded so that the cam follower I43 may move smoothlyalong the cam edge. Since the surfaces I I-I and MI are circular, it isevident that as long as the cam follower I43 rides along one of thesesurfaces, the prisms 35 and H5 respectively will remain stationary. Asthe follower 43 crosses a corner such as I44, the prism will turnthrough a small definite angle and again remain stationary until thenext corner is reached. When the edg I is reached, the

prism instantaneously re-sets itself under the influence of its springs53' to its initial position. Therefore, with the use of such a cam, theimage surfaces at transmitter and receiver are scanned by colors whichremain unvarying throughout the fraction of the scanning cyclerepresented by the portion of a complete circumference which each of thesurfaces I il and MI cover. Thus, if the number of scanning cycles for agiven circular line about the transmitting and recording drum is reducedand the cam I4I utilized, the image surface will be scanned by asuccession of fixed colors.

It is important to note that when this modification is utilized, thatthe number of drum rotations corresponding to a single revolution of thecam is equal to the number of sectors into which the'cam MI is divided.

For finer color reproductions, it is, of course, evident that the numberof revolutions of the drum corresponding to a single circular scanningline may be increased. However, such a procedure lengthens thetransmission time and I have found that a suitable compromise betweenexcellent reproduction and rapid transmission time is eight completerevolutions of the drum for each circular line. Evidently, variousmodifications of this color scanning system may be devised.

For example, the prisms 35 and H5 may be oscillated by variouselectro-mechanical means rather than the cam mechanism described.

The light valve I22 at the receiver, Figure 2, may of course be disposedin the position indicated or between the vertical slit H3 and thecylindrically ground lens H5. The light valve I22 must also be chosen,such that it does not affect the color transmission characteristic ofthe scanning optical system illustrated in these figures.

The cam may be modified in any suitable way; thus, for instance, it mayhave three steps arranged for the red, yellow and blue portions of thespectrum, in which case each line need be scanned only three times; itmay have more than eight steps or an infinite number as shown in Figures1 and 2. And the drum may be caused to rotate three revolutions perhelical line, eight revolutions or any other number. The slightoverlapping of the lines as the drum moves longitudinally avoids sharpstriations on the film.

Also, it will be obvious that the transmitter and receiver may becombined in a single unit with means for shifting the light valve out ofposition and locking the clutch when the device is used as atransmitter.

Various mechanisms may of course be utilized to scan the drum attransmitter and receiver in the manner described. Of course, helicalscanning of the recording and transmitting drum may be utilized insteadof the intermittent type of circular scanning. If helical scanning isused, then the various colors used at transmitter and receiver forscanning the image surfaces may overlap from line to line, but this ofcourse will not afiect color rendition, but will slightly afiect thedetail of the reproduced picture.

Accordingly, various modifications of this type of color facsimilesystem will be evident to those skilled in the art. I do not wish to bebound by the above specification and drawings, but only by the appendedclaims.

I claim:

1. In a, facsimile transmitter, a scanning de-- vice, comprising a drumupon which a picture is mounted, and a motor mechanism for rotating saiddrum in a predetermined manner; means for inducing longitudinal motionof said drum, a White light source, a prism, means for focusing lightfrom said source on said prism, said prism separating the light into aspectrum, means for focusing said portion on an element of said picture,means comprising a, lens system and photo cell for converting lightreflected from said picture into electric currents; and means comprisingmechanical linkages operably connected to said motor mechanism foroscillating said prism to present each portion of said spectrum to saidmeans for selecting a said portion of said spectrum in a predeterminedmanner, said drum being arranged to rotate and translate axially in sucha manner that each said portion of said spectrum scans each element ofsaid picture once.

2. In a facsimile receiver, a scanning device comprising a drum uponwhich a sheet of color selective light sensitive paper is mounted, and amotor mechanism for rotating said drum in a predetermined manner andmeans for inducing axial translation of said drum; a White light source,a prism, means for focusing light from said source on said prism, saidprism separating the light into a spectrum, means for selecting aportion of said spectrum, means for focusing said portion on an elementof said sensitive paper, means comprising a, light valve for controllingthe intensity of said portion in accordance with an electric current;and means comprising mechanical linkages operably connected to saidmotor mechanism for oscillating said prism to present each portion ofsaid spectrum to said selecting means in a predetermined manner insynchronism with rotative movement of said drum; said drum beingarranged to rotate and translate axially in such a manner that each saidportion of said spectrum, controlled in intensity by said light valve,scans each element of said sensitive paper once.

3. In a facsimile system, a, transmitter comprising means for separatinga picture into a series of elements, means for selecting each saidelement in turn according to a predetermined plan, means for separatingeach of said elements into its various colors, means for generatingelectric currents in accordance with the intensity of each of saidcolors, and a receiver comprising a source of White light, means forseparating said light into a spectrum, means for selecting a portion ofsaid spectrum, means for exposing the elements of a sheet of lightsensitive paper to said portion of said spectrum, means for controllingthe intensity of said portion in accordance with electric currentsgenerated by said transmitter, means for exposing each element of saidsensitive paper to said portion of said spectrum in turn according to apredetermined plan, means for coupling said transmitter to saidreceiver, and means for synchronizing said transmitter with saidreceiver so that corresponding elements of said sensitized paper andsaid picture are juxtaposed to their respective light sources at alltimes and corresponding portions of said spectra are presented to theirsaid selecting means at all times.

WILLIAM G. H. FINCH.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,010,307 Leishman Aug. 6, 19352,278,940 Murphy Apr. 7, 1942 2,193,606 Ulrey Mar. 12, 1940 2,297,524Anderson Sept. 29, 1942 2,343,971 Goldsmith Mar. 14, 1944 2,297,444 VonBronk Sept. 29, 1942 2,099,889 Ives Nov. 23, 1937

